Chemical sensors that identify and monitor volatile organic compounds (VOCs) have an important role in assessing public security, food and water quality, industrial environment, and health. For example, the detection of residual volatile organic compounds (VOCs) in consumer goods such as food, shelter, clothing, and medicine and to protect workers from occupational exposure is desirable. Presently, monitoring and determination of the chemical components of gas samples is typically performed using expensive gas chromatography-mass spectrometry (GC-MS) which has limited portability and requires highly trained users.
Carbon nanotubes (CNTs), are useful materials in chemical sensing as a result of the sensitivity of their electrical conductance to the presence of chemical analytes. For example, CNTs may be covalently or non-covalently functionalized with polymers, metals, or small molecules to enhance the selectivity and sensitivity of these materials to specific analytes. However, dependence on expensive specialized equipment for the fabrication of devices, the need for solution processing, and requirements for chemical functionalization for achieving specificity have limited the applications and wide applicability of these materials. For example, carbon nanotubes (CNTs) are promising materials for sensing of gases and volatile organic compounds; however, their poor solubility in most solvents has hindered the solution-based process of covalent or non-covalent chemical functionalization of CNTs, and the subsequent integration of these materials into devices. Additionally, methods for fabricating devices with CNTs are often expensive and time-consuming. For example, covalent and non-covalent functionalization of CNTs to generate selective sensing materials in solution often takes hours and sometimes days. Integration of these materials into devices by drop casting, spin coating, and inkjet printing typically requires prolonged drying times to remove solvent, and often involves several repeated processing cycles to obtain devices with desired electrical properties. Furthermore, known methods for fabricating such devices often require the use of toxic solvents, surfactants, or prolonged sonication for dispersing materials in solution.